The state of Oklahoma is served by the following area codes:
Area codes 705, 249, and 683 are telephone area codes in the North American Numbering Plan (NANP) for most of northeastern and central Ontario in Canada. Area code 705 was created in a 1957 area code split from portions of the 613 and 519 numbering plan areas. After a reduction in geographic coverage in 1962, the numbering plan area was assigned a second area code, 249, in 2011 to form an overlay numbering plan. A third area code, 683, was added in June 2022.
Area codes 905, 289, 365, and 742 are telephone area codes in the North American Numbering Plan (NANP) for the Golden Horseshoe region that surrounds Lake Ontario in Southern Ontario, Canada. The numbering plan area (NPA) comprises (clockwise) the Niagara Peninsula, the city of Hamilton, the regional municipalities of Halton, Peel, York, Durham, and parts of Northumberland County, but excludes the City of Toronto.
In telecommunications, an overlay plan is a telephone numbering plan that assigns multiple area codes to a geographic numbering plan area (NPA). Overlaying numbering plan area codes is practiced in territories of the North American Numbering Plan (NANP) to prevent exhaustion of telephone numbers and central office codes in growth areas.
Area codes 514, 438, and 263 are telephone area codes of the North American Numbering Plan (NANP) for Montreal and most of its on-island suburbs, specifically the Island of Montreal and Île Perrot in the Canadian province of Quebec.
Area codes 208 and 986 are the area codes in the North American Numbering Plan for all of Idaho. Area code 208 is one of the 86 original area codes created by AT&T in 1947. It was Idaho's sole area code until 2017, when 986 was added as an overlay plan for the entire state.
Area code 250 is a telephone area code in the North American Numbering Plan (NANP) for the Canadian province of British Columbia outside the Lower Mainland, including Vancouver Island–home to the provincial capital, Victoria–and the province's Interior region. In addition, the numbering plan area extends into the United States community of Hyder, Alaska, located along the Canada–United States border near the town of Stewart. The incumbent local exchange carriers that service the area code are Telus, Northwestel, and CityWest in the city of Prince Rupert.
Area codes 778, 236, and 672 are telephone area codes in the North American Numbering Plan (NANP) for the entire Canadian province of British Columbia. They form an overlay complex with area code 604, which serves only a small southwestern section, the Lower Mainland, of the province, and area code 250, which serves the rest of the province.
Area code 780 is a telephone area code in the North American Numbering Plan (NANP) for the Canadian province of Alberta. The numbering plan area comprises the northern two thirds of the province, including the Edmonton area. The area code was established in 1999 in a split of area code 403, which had served the entire province since the establishment of the original North American area codes in 1947. The numbering plan area is also served by area codes 587, 825, and 368, which form a complex overlay for all of Alberta.
Area code 604 is a telephone area code that serves southwestern British Columbia, Canada: the Lower Mainland, Sunshine Coast, Howe Sound / Sea to Sky Corridor, Fraser Valley and the lower Fraser Canyon regions. It primarily serves the city of Vancouver and surrounding regions.
Area codes 410, 443, and 667 are telephone area codes serving the eastern half of the U.S. state of Maryland, including the Baltimore metropolitan area and the Eastern Shore. The 410 area code is the original area code, while the 443 and 667 codes are overlay codes. 443 and 667 were primarily used with cellular phones and competitive local exchange carriers such as Comcast or Cavalier Telephone when introduced but have since become universal in their carrier availability.
Area codes 860 and 959 are telephone area codes in the North American Numbering Plan in the U.S. state of Connecticut. They are arranged in an overlay plan that covers most of the state, except its southwest, which uses area codes 203 and 475.
Area codes 303, 720 and 983 are telephone area codes in the North American Numbering Plan for the north-central portion of the U.S. state of Colorado. The numbering plan area comprises Denver and Boulder, as well as their surrounding suburbs, including Lakewood, Littleton, Longmont, Broomfield, Aurora, and Castle Rock. Area code 303 is the original area code, while area codes 720 and 983 were added to form an overlay plan for the area, meaning that the same geographic service area is served by all area codes and that ten-digit dialing is required for all calls made within the service area.
Area codes 405 and 572 serve the central part of the U.S. state of Oklahoma. They cover Oklahoma City and most of its suburbs, including Edmond, El Reno, Norman, Stillwater, Shawnee, Chickasha, Tuttle, Moore, and Guthrie.
Area code 816 is a telephone area code in the North American Numbering Plan (NANP) for Kansas City, St. Joseph, and all or part of 15 surrounding counties in northwestern Missouri. The numbering plan area originally comprised most of the northern and western two-thirds of the state, bordering with Arkansas, Illinois, Iowa, Kansas, Nebraska, and Oklahoma, but has been reduced to a ribbon bordering Kansas. 816 is one of the original 86 area codes created in 1947.
Area codes 918 and 539 are telephone area codes serving Tulsa and northeast Oklahoma. Besides Tulsa, these area codes cover cities such as Bartlesville, Broken Arrow, Claremore, Gore, Jenks, McAlester, Muskogee, Okmulgee, Pryor, Sapulpa, Tahlequah, and northeastern Oklahoma.
Area code 580 serves most of southern and western Oklahoma, including Ada, Boise City, Lawton, Enid, Fairview, Ponca City, Altus, Frederick, Weatherford, Guymon, Durant, and Ardmore.
Area codes 587, 825, and 368 are telephone area codes in the North American Numbering Plan (NANP) for the entire Canadian province of Alberta. They form an overlay with both of the previously existing area code 403 of southern Alberta, and northern Alberta's 780. Telephone numbers in area code 587 were allocated starting in late 2008. The complex overlay involving a total of five area codes in Alberta mandated ten-digit dialing throughout Alberta.